Paul Malignaggi comprehensively out-pointed champion Lovemore N'dou to take the IBF light welterweight title.
Malignaggi succeeded in his second attempt at a world title
Malignaggi, 26, used his speed and quickness to keep N'dou at bay on his way to his 23rd win in 24 fights.
He landed a left-hook counter in the ninth round to score the fight's only knockdown. Two judges scored it 120-106 while the other made it 118-108.
The loss snapped a six-fight winning streak for N'dou, who captured the IBF title in Australia in February.
It was American Malignaggi's second title bout, almost a year after the 26-year-old from New York lost a unanimous decision to Miguel Cotto for the WBO version of the title.
"I have something to strive for now. I can strive to fight Cotto again one day," he said.
"It gives me a new goal to strive to win and look really impressive before anyone can even think I deserve a rematch."
Malignaggi's best weapon was his jab, which he landed often throughout the fight. He also threw several combinations that landed, and was the more effective counter-puncher.
N'dou, 35, spent a majority of the bout pursuing Malignaggi, but most of his punches were blocked.
A frustrated N'dou (45-9-1) had a point taken away in round six after repeatedly hitting Malignaggi in the back of the head.
But he landed one good right hand in round eight, his best round of the fight.
Erdei dominated the bout from the first bell
In Budapest, Zsolt Erdei stopped George Blades in the 11th round to retain his WBO light heavyweight title.
Referee Joe Cortez called a halt after the Hungarian unleashed a flurry of blows and staggered his American opponent with a right hook.
It was Erdei's eighth successful title defence since winning the belt in January 2004 in a unanimous decision over Mexico's Julio Cesar Gonzalez.
He improved to 27-0 (17 KOs) in his first fight on home soil since 2004.
"It wasn't as easy as it looked and I lost my breath a couple of times, but I quickly regained my momentum each time," Erdei said.
"I think the referee had enough of my opponent getting soundly beaten and he was right to stop the fight."